1. Field of the Invention
The invention relates to a method for low-pressure locking of a gas-filled device, wherein a steering movement of a pressure detector in association with a gas tank in the device causes interruption in the connection between a blocking means connected thereto and a locking means in the low-pressure locking device, a shift being caused in the locking means leading it to the path of motion of a locking plate connected to a steering shaft in the device in order to limit the movements of the locking plate.
2. The Prior Art
Such low-pressure locking is used, e.g., in transmission of electricity in association with a gas-filled switch disconnector, wherein the low-pressure locking monitors and sees to it that the gas pressure in the shielding-gas-filled switch disconnector continuously remains on an operational level. A gas pressure drop in such a switch disconnector causes environmental risks when the disconnector is being used. When the gas protecting the operation of the switch disconnector disappears or the pressure drops unfavourably, the device may explode if attempts are made to use it for switching.
It is known to use low-pressure locking in such a device to prevent the use of a switch disconnector if the pressure of the gas protecting the operation drops below an allowed limit, so that the tripping of the low-pressure locking prevents the switching from being done.
If this kind of a low-pressure locking connected to a gas space is tripped, the gas pressure in the switch disconnector tank has to be checked and gas has to be added when required. Similarly, after each tripping of the low-pressure locking, the locking mechanism has to be charged.
A problem with the low-pressure locking of known devices is, however, that low-pressure locking can be tripped also because of other reasons than a pressure drop caused by gas leakage. Thus, the pressure in the gas space of such a device is dependent on the temperature variations on site, and the tripping pressure activating the low-pressure locking is again dependent on the external pressure on site.
In this case temperature variations on site affect gas pressure in the gas space of the device so that a temperature drop causes the gas in the gas tank to contract leading to a pressure drop therein. This pressure drop may cause "unnecessary" tripping of the low-pressure locking. These problems are encountered when a device is used in regions with significant temperature variations, e.g. deserts, or regions with extremely low seasonal temperatures, such as Nordic wilds.
Variations in the external pressure of the gas space affect in turn the tripping pressure so that when the device is used in high atmospheric pressure, the tripping pressure of the device approaches the pressure in the gas space causing unnecessary tripping of the low-pressure locking.
Tripping of a low-pressure locking causes severe problems to the user of a power supply network as it is extremely laborious to charge known solutions intended to handle the locking. Thus, to charge the low-pressure locking, the electric line in the vicinity of a switch disconnector has first to be de-energized, and then service personnel have to get to the device and, after partial disassembly of the device, manually charge the low-pressure locking so that it can be reused. As devices using low-pressure locking are often situated extremely inconveniently, and even mounted on power poles clearly above ground level, to access and service them is laborious and time-consuming.
It is an object of the present invention to eliminate the disadvantages of known solutions and provide a new kind of solution for allowing reparation of erroneous operation due to external pressure and temperature variations by using remote control. The present invention also ensures operation of low-pressure locking by eliminating oxidation of its switching surfaces and resulting breakdown.